Epifaunal biodiversity of gorgonians from the South of Portugal

• Autor(a) principal: Dias, Maria Inês Rocha Maia
• Data de Publicação: 2012
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/12501
• topic: Biologia marinha; Ecossistemas aquáticos; Gorgónias - Algarve (Portugal); Bentos

Gorgonians are sessile cnidarians with a three-dimensional and complex structure that plays a relevant ecological role in coastal ecosystems, providing physical habitat, refuge and food sources for other small organisms. Despite their relevance as foundation species, very few studies have addressed the ecological patterns of hosts (gorgonians) and their attendant fauna. The present study aims to analyse the temporal variability of the epifaunal assemblages associated with two of the most abundant gorgonian species from southern Portugal, Eunicella gazella and Leptogorgia lusitanica. As gorgonian populations comprise colonies of different sizes, ecological patterns of attendant assemblages were also analysed with regards to colony size (3 size classes). Replicate samples were collected in July and November 2010, March, June and August 2011 in Pedra da Greta (Algarve, Portugal). The results suggest that the gorgonian host exert a significant effect on the composition and structure of the attendant epifaunal assemblages, although most taxa were common to both hosts. Time, more than size, was found to be a main driver of the ecological patterns of these assemblages, where amphipods, molluscs and polychaetes were the more abundant and richest groups. The temporal patterns were characterized by high densities and diversity in the attendant epifaunal assemblages during spring-summer, followed by a high mortality or emigration of rare and occasional taxa, leading to a sharp decrease in the values of biodiversity and abundance indicators. During the autumnwinter period, the assemblages were mainly dominated by the resident taxa (i.e. taxa present in all sampling dates). After the peak of phytoplankton observed during this period and as the seawater temperature increased, the spring recolonization contributed to the re-establishing of rich and abundant assemblages that persisted during the summer. Therefore, temporal variability must be taken into account for the design of future biodiversity assessment studies, as different patterns may be observed depending on the sampling time.